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Chapter 21: The Lymphatic & Immune Systems - Coggle Diagram

- - - - Lymph Capillaries
        
        Smallest lymph vessels
        
        First to receive lymph
        
        Receive tissue fluid from connective tissue
        
        When volume of tissue fluid increases, mini-valve flaps open & allow fluid to enter
        
        Are highly permeable vessels
        
        Allow entrance of tissue fluid & protein molecules, bacteria, viruses & cancer cells
        
        Located near blood capillaries
        
        Lacteals
        
        Specialized lymphatic capillaries
        
        Located in the villi of the small intestines
        
        Receive digested fats
      - Collecting lymphatic vessels
        
        Collect from lymph capillaries
        
        Lymph nodes are scattered along collection vessels
        
        Accompany blood vessels
        
        Composed of the same 3 tunics as blood vessels
        
        Contains more valves than veins do
        
        Helps direct flow of lymph
        
        Flow is not aided by heartbeat
        
        Lymph is propelled by 3 weaker mechanisms
        
        Lymph Nodes
        
        Cleanse the lymph of pathogens
        
        Human body contains ~500 nodes
        
        Superficial lymph nodes located in:
        
        Cervical region
        
        Axillary region
        
        Inguinal region
        
        Where Lymph Nodes Drain
        
        Left Thoracic Duct
        
        Lymph nodes everywhere in the body (except right arm, right thorax & right upper abdomen) drains to the left thoracic duct
        
        Right Lymphatic Duct
        
        Lymph nodes in the right arm, right thorax & right upper abdomen drains to the right lymphatic duct
        
        Microscopic Anatomy
        
        Fibrous Capsule
        
        Surrounds lymph nodes
        
        Trabeculae
        
        Connective tissue stands extend inward to divide lymph node into segments/lobules
        
        Afferent Lymphatic Vessels
        
        How lymph enters convex aspect of a lymph node
        
        Many entrance pathways
        
        Efferent Lymphatic Vessels
        
        How lymph exits a lymph node
        
        At the hilum
        
        3 Weaker Propelling Mechanisms
        
        Bulging of skeletal muscles
        
        Pulsing of nearby arteries
        
        Tunica media of the lymph vessels
      - Lymph Trunks
        
        Collect lymph from collecting vessels
        
        5 major lymph trunks
        
        Lumbar Trunks
        
        Receive lymph from lower limbs
        
        Intestinal Trunks
        
        Receives fatty lymph from digestive organs
        
        Bronchomediastinal Trunks
        
        Collects lymph from thoracic viscera
        
        Subclavian Trunks
        
        Receive lymph from upper limbs & thoracic wall
        
        Jugular Trunks
        
        Drain lymph from the head & neck
      - Lymph Ducts
        
        Empty into veins of the neck
        
        Cisterna Chyli
        
        Located at the union of lumbar & intestinal trunks
        
        Thoracic Duct
        
        Ascends along vertebral bodies
        
        Empties into venous circulation
        
        Junction of left internal jugular & left subclavian veins
        
        Drains 3 quarters of the body
        
        Right Lymphatic Duct
        
        Empties into right internal jugular & subclavian veins
- - - - Thymus
        
        Site where immature lymphocytes develop into T lymphocytes
        
        Secretes thymic hormones
        
        Most active in childhood
        
        Functional tissue atrophies with age
    - - Lymph Nodes
        
        Function:
        
        Lymph percolates (filters) through lymph sinuses
        
        Most antigenic challenges occur in lymph nodes
        
        Antigens destroyed & activate B and T lymphocytes
      - Spleen
        
        Largest lymphoid organ
        
        2 main blood-cleansing functions
        
        Removal of blood borne antigens
        
        Removal & destruction of old or defective blood cells
        
        Destruction of antigens
        
        Site of B cell maturation into plasma cells
        
        Phagocytosis of bacteria & worn-out RBCs, WBCs & platelets
        
        Storage of platelets
      - Tonsils
        
        Simplest lymphoid organs
        
        4 groups of tonsils
        
        Palatine, lingual, pharyngeal & tubal tonsils
        
        Arranged in a ring to gather & remove pathogens
        
        Underlying lamina propria consists of MALT
      - Aggregated Lymphoid Nodules & Appendix
        
        MALT is abundant in walls of intestines
        
        Fight invading bacteria
        
        Generate a wide variety of memory lymphocytes
        
        Aggregated Lymphoid Nodules
        Peyer's Patches
        
        Located in the distal part of the small intestine
        
        Appendix
        
        Tubular offshoot of the cecum
  - - - B Lymphocytes
        
        Become plasma cells
        
        Secrete antibodies, which mark cells for destruction by macrophages
        
        Respond primarily to bacteria & bacterial toxins
      - Natural Killer (NK) Cells
        
        Don't recognize specific antigens
        
        Natural killer (NK) cells patrol the body
        
        Detect & destroy the virus-infected cells & early-stage cancers
        
        If a host cell loses its healthy "self-markers" or displays stress signals, the NK cells triggers cell death
      - Cytotoxic T Lymphocytes
        
        Attack foreign cells directly
        
        Bind to [not self-]antigen-bearing cells
        
        Perforate cell membrane
        
        Signal cell to undergo apoptosis
        
        Destroy virus-infected cells & some cancer cells
    - - Activated Lymphocytes
        
        Able to recognize a unique antigen
        
        Gain immunocompetence
        
        Travel through bloodstream
        
        Meet & bind to a specific antigen
        
        Proliferate rapidly
      - During Activation
        
        Lymphocyte is presented its specific antigen via an antigen presenting cell: macrophage or dendritic cell
        
        Takes pieces of the pathogens & presents it on its surface
        
        This is what introduces the lymphocyte to the antigen for the very fist time
      - T & B Lymphocytes
        
        Produce clones of effector lymphocytes & memory cells
        
        Effector Lymphocytes
        
        Respond immediately, then die
        
        Memory Cells
        
        Wait until the body encounters the antigen again
        
        Basis of acquired immunity
        
        Prevent subsequent infections of the same illness